Flight Risk

In space gamma rays—the most energetic forms of light—are created by violent events, such as supernovae, and powerful objects, such as neutron stars.

Scientists have known for decades that thunderstorms on Earth can also create gamma rays, possibly during lightning production. Storms that make gamma rays usually hover about 9 miles (15 kilometers) above Earth, about the same altitude at which many commercial planes fly.

The new study shows that just one of these terrestrial gamma ray flashes, or TGFs, can equal the radiation dosage of about 400 chest x-rays—creating potential hazards for frequent flyers. (Related: "Gamma Ray Burst Caused Mass Extinction?")

In theory, stray gamma rays can alter the structure of human DNA, possibly triggering cancer.

Still, much is unknown about TGFs, including how likely it is for an airplane to fly close to gamma ray sources in storms, noted study co-author Joseph Dwyer, a space scientist at the Florida Institute of Technology.

"I would put this pretty far down on the list [of airplane hazards]," Dwyer said. "I've worked a lot on this, and I would not hesitate to hop on an airplane and fly with my kids across the country."

In fact, people are probably at bigger risk just driving their cars, said Brant Carlson, a TGF expert at Stanford University in California.

"I would say this is a very, very unlikely event, much less likely than many other flight hazards, or the hazards involved in getting to the airport in the first place," said Carlson, who was not involved in the study.